142 



CONSCIOUS NERVOUS OPERATIONS 



vocal apparatus distribute the impulse to the necessary 

 muscles. In reading aloud it is the end organs for vision, 

 the eyes, which are first stimulated (Fig. 83); then the 

 impulse is carried to the visual center in the brain, from 



which nervous influences travel 

 by connecting nerve fibers to 

 the auditory word center. 

 There, as before, the sound of 

 the words is revived and the 

 impulse follows the path previ- 

 ously described. 



195. When a person writes 

 from dictation, another course 

 is followed (Fig. 84). The 

 auditory end organs of the 

 inner ear are first stimulated; 

 the impression travels by the 

 auditory nerves to the audi- 

 tory word center, then across 

 to the visual word center, 

 reviving there the appearance 

 of the words. Impulses pass 

 thence to the motor centers 

 and by motor nerves to the 

 various muscles of the arm 

 and hand involved in writing. 

 If nerve fibers which connect 

 the two word centers, visual 

 and auditory, arc diseased, nei- 



Fig. 83. Diagram of path of 

 nervous impulses in reading 

 aloud. 



Au C hearing center. 



OC sight center. 



Sp C speech center in left hemi- 

 sphere. 



V, VII, X, XI, XII, Sp If nerves 

 supplying motor fibers to the 

 speech organs: lips, tongue, 

 chest, etc. 



ther reading aloud nor writing from dictation is possible. 

 Vocalization may also be the result of reflex nervous 

 action, as when an involuntary scream follows sudden 

 fright. 



